The present invention relates generally to power semiconductor devices and, more particularly, to providing cooling for such devices.
Power semiconductor devices, such as insulated gate bipolar transistors (IGBT's), are used in a variety of applications that require high frequency switching of electrical power. These applications may include motor controllers or power converters. In many of these applications, heat may be generated in the device. It may become necessary to remove this generated heat from the device.
Typically, heat may be removed from the device with a heat sink. Heat sinks may be constructed from heat conductive material which may absorb heat for the device and then transfer the heat to a surrounding environment. For example, a heat sink may comprise a metal plate with cooling fins which allow heat to be dissipated by convection into air. In a more complex example, a heat sinking arrangement may comprise a heat conductor and a fluid flow system for extracting heat from the device. Fluid-flow cooling systems may comprise closed channels through which a cooling liquid may pass.
Prior-art heat cooling systems are typically designed with a cooling capacity that may accommodate a worst-case operating condition for the device. For example, if an assembly of IGBT's were to generate 100 watts during a brief peak operation, a cooling system may be provided to convey away at least 100 watts from the assembly. This illustrative peak cooling capacity may be incorporated into a design of a motor controller or power converter, even if steady-state operation produces only a fraction of the peak heating. Such a design principle may not be problematic in ground-based applications of IGBT's. But when IGBT's are employed in aerospace applications, space and weight become paramount design considerations.
In an aircraft or other aerospace vehicle, power converters and motor controllers may be subjected to widely varying operating conditions. Transient loads may greatly exceed steady-state loads. Prior-art cooling systems may be provided in anticipation of these high transient loads. Consequently, prior-art cooling systems may be space-consuming and may add undesirable weight to an aerospace vehicle.
As can be seen, there is a need to provide a small and lightweight cooling system for power semiconductor devices. In particular, there is a need to provide such a cooling system that may be only as large as a steady-state cooling system while also having capability for transient condition cooling.